Abstract

Monolith X is the latest addition to the Monolith product line, combining isothermal spectral shift detection with MST technology to characterize biomolecular interactions in solution. When a target is labelled with a fluorophore it generates a particular emission spectrum, and if a ligand binds to this labelled target, the fluorophore’s chemical environment is changed, causing a shift in fluorescence spectra. Monolith X exploits this phenomenon by performing ratiometric measurements at two emission wavelengths of a labelled target in the presence of various concentrations of an unlabelled ligand to derive the affinity constant (K_d) for the interaction.

 Isothermal spectral shift detection enables characterization of in solution interactions for a wide range of biomolecules, even for challenging samples such as membrane proteins, intrinsically disordered proteins, and cell lysates. Since the binding partners are in solution, there is no lost activity due to immobilization, and evaluation is size independent. Measurements can be performed in any buffer, including detergents, using low sample volumes and concentrations. The spectral shift analysis also facilitates the evaluation of competition assays and ternary binding events. Monolith X provides a valuable orthogonal method to validate your results from other biophysical methods and to characterize your most challenging interactions.